AFAIK there are no stopovers allowed, if you book a one way award.No stopovers allowed for award travel within the same region ( for example DUS-AMS-LHR would not allow a stopover in AMS )
However B 747 already mentioned that you can stop for 23:59 h on any international itenary....
I was also told that you must fly the most direct route, I don`t know how flexible they are when the most direct route is not available, though.* ( LH M&M )is very flexible with that, but I should not compare LH M&M SEN Service with KLM Plat Elite service.Without showing way too much patriosm that would be blasphemy...
The list of questions is more or less ready to be sent to KLM, so we will get answers to all our questions ( hopefully ) very soon.